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Hi,

I've been using mainly 06 mayco glazes and noticed the rim's on mugs chipping rather easily. I apply 3 coats of glaze to 04 bisque and not sure why I'm having this issue. 

Chipped off pieces are often very small. I dont think it's from the surface being too smooth for glaze to attach...

Please let me know what possible issues thanks so much ! 

 

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Pictures for sure on this one. Is this before firing, after firing? If after did the base claybody chip with the glaze or just the glaze? Is this commercial glaze or a mixed from a recipe? Does it look like it fired to maturity? Lots of questions, I think we really need pictures to render a decent opinion.

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@Tsculpt, the reason we are all asking for photos of the chipping is because it could well be shivering thats happening. Shivering is when there isn't a good fit between the clay and the glaze and sharp little shards of glaze either spontaneously break off (usually on rims or edges) or it can happen when rims or edges are tapped. Shivering is obviously dangerous, especially with functional ware, can't tell without a photo if it might be that or simply chipping from a weak underfired body or glaze.

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Thanks for posting the picture, yes, that is shivering. Unfortunately there is nothing you can do to save these mugs, they would be dangerous to use and should be smashed prior to disposing of them. Shivering is the opposite of crazing, the glaze is under too much compression and flakes/chips away from the body. Since you are using a commercial glaze we can't offer a fix for the glaze recipe but you are going to need to try a different glaze or a different claybody. Clay and glaze need to "fit" each other. I'ld suggest just buying a small amount of a different line of glaze and make up some quick simple cylinders (they can just be thin and rough, don't need a base). Glaze them thickly in whatever glaze you want to test then fire as usual. Tap them with the something dense like a screwdriver handle and see what happens. Hopefully your next glaze won't have this fit issue. If you are in love with this glaze then try another clay body.

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13 hours ago, Tsculpt said:

invested so much into these glazes it would be better to switch clay at this point. 

If that's the most economical.

It very well could be a faulty batch or box of clay. Or perhaps just one of the glazes.

The bad thing is the rest of that batch may be sitting unused in a school somewhere right now, so there may be no word of it being bad.

Truth truth, with all "yes it is shivering" in mind for safety, I'm still not convinced. Since according to the text, it could still be them chipping when bumped.

No sense chasing gremlins.

Sorce

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Interesting in that it looks like underglaze was used to more solidly accent the rim area as well. Most commercial glaze folks will say they only test with all their product for compatibility. Is that Mayco underglaze?

Seems the chipped  areas have lost their underglaze  as well.

Edited by Bill Kielb
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It can be many things but a change of clay or underglaze is easiest. Testing needs to happen after that-All the pots you made need to be destroyed as they are unsafe. Real bummer

part of the journey-happens to us all sooner or later.

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where i order clay from suggested to gloss fire to cone 05 instead of 06 but would this really solve the issue?

also wondering if it could be an application error on my part. 

however looking into switching clay all together to find one that fits these glazes best

thanks!

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I am wondering, if you compressed the rims when throwing them, did you use a chamois or other method to compress the rim. If you used a sponge, the clay particles and grog get exposed and do not have as much body adhesion on the rim.   Just a thought,

best,

Pres

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thanks all but i do not use underglazes. Ive been using mayco foundation glazes and it is always the black that chips. i have had more then 1 container of black and also had 2 different lots of white clay. 

I talked to my ceramic supplier they told me to gloss fire at 05 instead of 06. 

I then talked to Mayco directly they told me never to do 05 instead of 06 for the gloss fire. Then also stated that standard 105 clay is a recommended clay for their brand. 

Im pretty overwhelmed.  Sorta just getting the run around. 

Really wondering if i just need to do a overall thicker application to solve the issue. but honestly at this moment I think im just going to look into high fire clay for dinnerware because i dont want to put anyone at risk if this is going to keep happening. 

 

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30 minutes ago, Tsculpt said:

i have had more then 1 container of black and also had 2 different lots of white clay. 

What did Standard say when you let them know about the shivering? Did you give them the lot numbers? Could be that you got some that wasn't mixed properly.

30 minutes ago, Tsculpt said:

Really wondering if i just need to do a overall thicker application to solve the issue. but honestly at this moment I think im just going to look into high fire clay for dinnerware because i dont want to put anyone at risk if this is going to keep happening. 

Thicker will just make the shivering worse. Shivering can happen with any claybody but is most common with white lowfire bodies and isn't very common with mid and high fire. Advantage of going to a midrange claybody for functional ware is if you choose a clay that has less than 2% absorption then you won't have issues with pots getting hot in the microwave, crazing and weeping from moisture seeping into the clay and they tend to chip less than lowfire.

30 minutes ago, Tsculpt said:

I then talked to Mayco directly they told me never to do 05 instead of 06 for the gloss fire.

I think this is a bit of a red herring, many kilns don't fire evenly, especially older large manual ones. It would be easy to get to 05 in the middle of the kiln and 06 in the cooler parts near the floor or lid.

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1 minute ago, Babs said:

Thicker won't do it..

Test tiles only way to go 

so i have many test tiles, never had an issue with chipping/shivering. it seems only specific pieces are effected by this. i went back to check a number of lips on mugs and bowls and its either they are completely fine or will chip off when tapped against another.

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